Integral water resistant fibre-cement

ABSTRACT

A method of producing a water resistant fibre-cement product. The water repelling agent can be added or applied to the fibre-cement or indeed the material forming the fibre cement at a number of different stages in the process. The resultant material has increased water impermeability over conventional fibre-cement products.

FIELD OF THE INVENTION

[0001] This particular invention relates to a water resistant cement.More particularly the invention relates to the preparation and use of awater resistant fibre-cement product to produce fibre-cement boardcladding, tiles and/or panels.

BACKGROUND OF THE INVENTION

[0002] Fibre-cement products which may include board tiles and/or panelsare commonly used in the building industry in the manufacture ofsidings, exterior cladding, skirting and interior panels, and many otherinterior construction materials. In the industry, fibre-cement board mayalso be known as “fibreboard”.

[0003] The problem with fibre-cement products is that if water entersthe product (eg a wall panel) before installation, the panel will expandslightly and, if installed, stress will build up in the panel as itdries that can lead to bowing and like problems. Thus it is clearlydesireable that the fibre-cement product be water-resistant or waterrepelling to combat such problems.

[0004] The difficulty in producing water resistant fibre-cement productshas been primarily due to the harsh conditions used during thepreparation of the fibre-cement product. To increase its flexuralstrength, fibre-cement products are normally cured in an autoclave. Thesaturated steam pressure used-is usually about 1000 KPa. The pressure isheld at this level for approximately 8 hours, and the alkalinity of theboard may be as high as a pH of 13. These harsh conditions affect themolecular integrity of the organic polymers used and this prevents theformation of water resistant fibre-cement.

[0005] Whilst many different hydrophobic polymers have been successfulat waterproofing building materials, such as gypsum, they have failed toimpart water resistance on fibre-cement products primarily due to theproblems of the autoclaving process used for fibre-cement production.

[0006] In this specification, the relationship between a water repellingagent and fibre-cement is described by the term “integrally associated”.This term is understood to describe the substantially even spread ordistribution of a water repelling agent throughout the fibre-cement.

OBJECT OF THE INVENTION

[0007] It is an object of the present invention to overcome orameliorate the disadvantages of known fibre-cement products, or to atleast provide the public with a useful alternative.

[0008] Other objects of the invention may become apparent from thefollowing description which is given by way of example only.

SUMMARY OF THE INVENTION

[0009] According to one aspect of this invention there is provided amethod of producing a water resistant fibre-cement product, the methodincluding combining a water repelling agent with a fibre-cementmaterial; forming a fibre-cement product from the combination, wherebythe water repelling agent is integrally associated with thefibre-cement.

[0010] Preferably, the water repelling agent is a long chain terpolymerderived from ethylene, vinyl chloride, and/or vinyl laurate.

[0011] Preferably the terpolymer includes silane based functionalgroups.

[0012] In one preferred form the water repelling agent is added to thefibre-cement as a dispersion and/or emulsion.

[0013] Preferably, the dispersion and/or emulsion includes the waterrepelling agent suspended water, or in an alkaline solution such as limewater.

[0014] Preferably, the water resistant fibre-cement product is a waterresistant fibre-cement board tile, panel, and/or exterior claddingmaterial.

[0015] Preferably the method includes the step of autoclaving thefibre-cement product.

[0016] According to a further aspect of this invention there is provideda water resistant fibre-cement, wherein the fibre-cement includes awater repelling agent that is integrally associated with thefibre-cement.

[0017] Preferably, the water repelling agent is a long chain terpolymerderived from ethylene, vinyl chloride, or vinyl laurate.

[0018] Preferably the terpolymer includes silane based functionalgroups.

[0019] Preferably, the water repelling agent is in a proportion ofsubstantially 0.5% to 10%, by weight of the total materials used toproduce the fibre-cement.

[0020] In one preferred form the water repelling agent is in aproportion of substantially 1%, by weight of the total materials used toproduce the fibre-cement.

[0021] In another preferred form the water repelling agent is in aproportion of substantially 7% by weight of the total materials used toproduce the fibre-cement.

[0022] Preferably, the water resistant quality of the product is notreduced by autoclaving.

[0023] Preferably, the product may be a tile, panel and/or exteriorcladding material.

[0024] In a further aspect the invention produces a process forproducing a water-resistant fibre-cement product, the method includingusing a terpolymer derived from ethylene, vinyl chloride, or vinyllaurate, in forming a fibre cement product wherein the terpolymer isintegrally associated with the fibre-cement, and autoclaving theproduct.

[0025] Preferably the autoclaving process includes the use of saturatedsteam at pressure, in an alkaline environment.

[0026] Preferably the saturated steam is at a pressure of about 1000KPa.

[0027] Preferably the alkaline environment is up to about pH 13.

[0028] Preferably the terpolymer is sprayed on to the fibre-cementduring formation of the fibre-cement.

[0029] In a final aspect the invention relates to a water-resistantfibre cement board produced by any-one of the above processes.

[0030] Other aspects of the invention will become apparent from thefollowing description which is given by example only and with referenceto the drawing.

BRIEF DESCRIPTION OF THE DRAWING

[0031] The invention will now be described by way of example only andwith reference to the drawing in which:

[0032]FIG. 1: is a schematic flowchart of a process for the preparationof fibre-cement board tiles and/or panels according to the invention.

[0033]FIG. 2: is a comparison of a water resistant board according theinvention (Monotek) in comparison with other comparable availablefibreboard products.

DETAILED DESCRIPTION OF THE INVENTION

[0034] The invention described herein relates to water resistantfibre-cement and/or water resistant fibre-cement products. The inventionalso relates to a process for preparing water resistant fibre-cement andits use to produce water resistant fibre-cement products.

[0035] Water resistant fibre-cement products are used in a wide range ofbuilding and construction material, such as exterior and interiorcladdings, panels and/or tiles, planks, building boards-and the like. Itwill be understood that the term “water resistant fibre-cement product”is used in a general sense herein and is not limited to a specificconstruction or building material.

[0036] The water resistant fibre-cement product is constructed,including water repelling agent and fibre-cement.

[0037] The fibre-cement is composed from fibre, binder and otheradditives as will be known in the art. The fibre-cement provides theproduct with strength and stability by retaining the product in thedesired form.

[0038] The water repelling agent is in a proportion of about 0.5 wgt %to 10 wgt %. The proportion of the water repelling agent may be variedin accordance with the specific use for a water resistant fibre-cementproduct. For example, a fibre-cement product for use as an interiorsurface in wet areas, such as a kitchen, will preferably include about0.5 to 2 wgt % of the water repelling agent.

[0039] A fibre-cement product for use as an exterior cladding or in awet wall area may include between about 0.5 and 2% preferably 1 wgt % ofthe water repelling agent. Alternatively where a water resistantfibre-cement product is intended to be used as a roofing product, ahigher proportion, between about 2-10%, preferably about 7 wgt %, of thewater repelling agent is used.

[0040] Where a water resistant fibre-cement product is to be used as anexterior tile or panel, it is also desirable to include a highproportion of the water repelling agent. This may also range from 2 wgt% to 10 wgt %. Thus, the proportion of a water repelling agent includedin the water resistant fibre-cement product may be tailored to thespecific end use of a water resistant fibre-cement product.

[0041] A water resistant fibre-cement product may be prepared for ageneral or all purpose application. In this case the quantity of thewater repelling agent is not dictated by the final use for the waterresistant fibre-cement product. Thus, the quantity of water repellingagent in an all purpose water resistant fibre-cement product ispreferably in the range of about 2 wgt % to 10 wgt % preferably betweenabout 4 and 7 wgt %.

[0042] The water repelling agent will be integrally associated with thefibre-cement in the water resistant fibre-cement product. Thus, thewater repelling agent will be dispersed evenly throughout the waterresistant fibre-cement product. This means the product as a whole isresistant and surface damage will not affect performance.

[0043] A further aspect of this invention includes the specificselection of unique water repelling agents for the production of a waterresistant fibre-cement. The selection of a particular water repellingagent to produce a water resistant fibre-cement may be dictated by anumber of factors including the stability of the water repelling agentduring the manufacture of water resistant fibre-cement and thesubsequent manufacture of the water-resistant fibre cement product; thestability of the water repelling agent's water repelling properties inthe water resistant fibre-cement product; and the long term stability ofthe water repelling agent in a water resistant fibre-cement product.

[0044] The water repelling agent should also be stable in the presenceof solvent based paints and/or residues which may be applied to thewater resistant fibre-cement product. In this preferred form, the waterresistant fibre-cement product should be capable of being subsequentlycoated with a range of solvents and water borne paints, and/or texturedcoatings. Therefore, the water repelling agent should be stable andsubstantially retain molecular integrity and/or avoid decompositionafter the application of paint coatings (or the like) to the waterresistant fibre-cement product. Alternatively the water repelling agentshould preferably retain water repelling qualities after the applicationof paint or solvent based coatings.

[0045] It has been surprisingly found that certain hydrophobicterpolymers derived from ethylene, vinyl chloride, and/or vinyl laurateare able to maintain water-resistant capability of the product can afterautoclaving to increase product strength. The terpolymers will, in apreferred form also include silane (silicon) functional groups. Suchcompounds produce a product that withstands the fibre-cement productionprocess and retains the water repelling properties product. This isparticularly surprising due to the harsh nature of the autoclavingprocess used to increase the strength of fibre-cement products (asdiscussed elsewhere herein). One particular product of use is VinnapasRI 554Z available from Waker Polymer.

[0046] A further aspect of the invention includes a method of producinga water resistant fibre-cement which may be used to prepare waterresistant fibre-cement products.

[0047] Water resistant fibre-cement and products thereof are producedthrough a number of steps. FIG. 1 illustrates the preferred preparationof water resistant fibre-cement products. It will however be appreciatedthat there may be a number of different ways to prepare fibre-cement andthe basic process described by FIG. 1 is known to produce fibre-cementproducts. The description given below with reference to the FIG. 1merely describes a preferred method of preparing water resistantfibre-cement and water-resistant fibre cement products.

[0048] With reference to FIG. 1, the initial water and fibre-cementmaking materials are mixed together in and by a mixing means 1. Thematerials may include fibre, binder, silica and additional componentsbeing included to optimise performance as are known in the art.

[0049] The water repelling agent can be added or applied to thefibre-cement (or material for forming the fibre-cement) at a number ofdifferent stages in the process.

[0050] In one preferred form, as shown in FIG. 1, the water repellingagent is added to the mixing means 1 during the mixing step of thefibre-cement making materials. In this form the water repelling agentmay be added in a number of ways. The water repelling agent may be addedas an emulsion and/or as an aqueous alkaline solution. A powder of thewater repelling agent may be pre-mixed with lime water or just water toform the emulsion/solution before it is added to the mixing means 1.Preferably the mixing time will be about 4 minutes.

[0051] Alternatively, the water repelling agent may be added as a groundpowder. In this way the powder is added to the mixing means 1, duringthe mixing of the fibre-cement making materials along with the othercomponents.

[0052] The way in which the water repelling agent is added to thefibre-cement making materials may also include pouring the waterrepelling agent, in one or more portions into the mixing means 1 eitherbefore or after mixing has commenced. Adding the water repelling agentsat this stage also assists in providing an even distribution of waterrepelling agents throughout the fibre-cement.

[0053] A slurry is produced from the initial mixing step in mixing means1 which is then drained into a buffer tank 2. In an alternative form,the water repelling agent could also be added to the slurry in buffertank 2 in one or more portions and mixed into the slurry.

[0054] Rotating sieves 3, housed within buffer tank 2, are suspendedpartially within the slurry in buffer tank 2 and accumulate slurrymaterial or fibre-cement on the sieves. The fibre-cement forms a thinlayer and/or crust around the outer surface of the rotating sieve 3. Therotating sieve 3 moves in the same direction to the rotating felt 4 withthe result that the fibre-cement on the sieve 3 accumulates on therotating felt 4.

[0055] In a further preferred form, instead of buffer the waterrepelling agent with the fibre-cement components, the water repellingagent may be sprayed onto the moving accumulated fibre-cement whichforms on the rotating sieves 3 or rotating felt 4. In this preferredform, an aqueous dispersion of the water repelling agent is sprayed ontothe newly accumulated fibre-cement while the rotating sieves 3 androtating felt 4 are rotating. Once the water repelling agent is sprayedon to the accumulated fibre-cement, the water repelling agent seeps intothe fibre-cement to become integrally associated with the fibre-cement.

[0056] The use of a spray to apply the water repelling agent alsoprovides a convenient way of varying the amount of water repelling agentapplied to the fibre-cement. A running speed of a spray delivery systemmay be tailored for operation with the rotating sieve 3 and rotatingfelt 4 so that the desired quantity of water repelling agent is appliedto the fibre-cement. It is also envisaged that the spray delivery systemmay be adapted so that the quantity of water repelling agent applied tothe fibre-cement may be varied.

[0057] The rotating felt 4 transports accumulated water resistant fibrecement, from the buffer tank 2 to the sheet machine 5. At the sheetmachine 5 excess water drains from the water resistant fibre-cement. Avacuum box may be used to facilitate this. The water resistantfibre-cement presented by the rotating felt 4 is pressed and/or cut by acutting machine 5 into an appropriate form for the desired use of thewater resistant fibre-cement product. The cutting machine 5 may beadjusted so that the water-resistant fibre cement product formed may bepanels, tiles and/or boards accordingly. It will be appreciated that thecircumference of the rotating sieve 3 dictates the length of the panelspresented by rotating felt 4.

[0058] The water resistant fibre-cement product, or green product,produced from the sheet machine 5 is then pre-cured at 6 which improvesthe green strength of the product so that it can endure the autoclaving.

[0059] Following the pre-curing treatment 6 the panels are thenautoclaved in autoclave 7 to increase the strength (eg flexuralstrength) of the product. The autoclaving process 7 is conducted at aspecific ratio of time to temperature, so that any growth of calciumsilicate hydrate crystals, which form the matrix of the board, can becontrolled.

[0060] The autoclaving process 7 typically operates with a saturatedsteam pressure level at substantially 1000 KPa. The autoclaving timecycle is substantially 8 hours. The autoclaving process 7 includes thesteps of, pressurising the autoclave chamber; holding the chamber at apressurised level; and finally venting the chamber after the requiredtime. During the process, the alkalinity of the water resistantfibre-cement product can be as high as a pH of 13. The water repellingagents herein described substantially withstand these harsh conditionsmaintaining water resistance in the water resistant fibre-cement productformed.

[0061] Finally the water resistant fibre-cement product produced istested in a laboratory 8; trimmed to shape and inspected forimperfections 9; and dispatched 10. varying the amount of waterrepelling agent applied to the fibre-cement. A running speed of a spraydelivery system may be tailored for operation with the rotating sieve 3and rotating felt 4 so that the desired quantity of water repellingagent is applied to the fibre-cement. It is also envisaged that thespray delivery system may be adapted so that the quantity of waterrepelling agent applied to the fibre-cement may be varied.

[0062] The rotating felt 4 transports accumulated water resistant fibrecement, from the buffer tank 2 to the sheet machine 5. At the sheetmachine 5 excess water drains from the water resistant fibre-cement. Avacuum box may be used to facilitate this. The water resistantfibre-cement presented by the rotating felt 4 is pressed and/or cut by acutting machine 5 into an appropriate form for the desired use of thewater resistant fibre-cement product. The cutting machine 5 may beadjusted so that the water-resistant fibre cement product formed may bepanels, tiles and/or boards accordingly. It will be appreciated that thecircumference of the rotating sieve 3 dictates the length of the panelspresented by rotating felt 4.

[0063] The water resistant fibre-cement product, or green product,produced from the sheet machine 5 is then pre-cured at 6 which improvesthe green strength of the product so that it can endure the autoclaving.

[0064] Following the pre-curing treatment 6 the panels are thenautoclaved in autoclave 7 to increase the strength (eg flexuralstrength) of the product. The autoclaving process 7 is conducted at aspecific ratio of time to temperature, so that any growth of calciumsilicate hydrate crystals, which form the matrix of the board, can becontrolled.

[0065] The autoclaving process 7 typically operates with a saturatedsteam pressure level at substantially 1000 KPa. The autoclaving timecycle is substantially 8 hours. The autoclaving process 7 includes thesteps of, pressurising the autoclave chamber; holding the chamber at apressurised level; and finally venting the chamber after the requiredtime. During the process, the alkalinity of the water resistantfibre-cement product can be as high as a pH of 13. The water repellingagents herein described substantially withstand these harsh conditionsmaintaining water resistance in the water resistant fibre-cement productformed.

[0066] Finally the water resistant fibre-cement product produced istested in a laboratory 8; trimmed to shape and inspected forimperfections 9; and dispatched 10.

[0067] It will be understood by persons skilled in the art that it isnot essential for the fibre cement product to be autoclave cured. Thewater resistant fibre cement product may be air cured if desired.

[0068] Spray application of polymer dispersions for the manufacture ofwater resistant fibre cement.

[0069] Mixing

[0070] The solid polymer powder is dispersed in water using a high speeddispersion blade. The solids content of the dispersion is typicallybetween 10 and 20% solids.

[0071] Spray Conditions

[0072] A spray bar was used with 4 to 6 jets, placed between 200 and 250mm above the felt. The jets are a fan jet type with a nozzle aperture of1 to 2 mm. The jets are arranged in two rows such that the spray patternfrom the jets in one row just overlaps the spray pattern from those inthe second row. The spray width is carefully controlled so that theoff-cut from the width trimming operation contains as little polymer asis possible. The spray pressure is typically 1 to 2 bars gauge pressure.The spray flow rate is typically 600 to 800 litres per hour.

[0073] Spray Bar Positioning

[0074] The spray bar was situated above the felt after the last sieveroller. The felt carries the wet fibre cement film the length of themachine to the accumulation roller where it is rolled into the filmsalready accumulated. When the desired thickness is achieved the wetboard, or green sheet, is cut off and sent to the trimming section viabelt conveyors.

[0075] Vacuum Box

[0076] During the transit time from the last sieve to the accumulationroller the polymer dispersion seeps through the wet film. At this pointthe film is typically 1.2 mm thick. Before the felt gets to theaccumulation roller it passes over a vacuum box. This provides adewatering effect that gives the film sufficient green strength to betransferred to the roller. The vacuum box also helps pull the polymerdispersion through the wet film, thus evening out the distribution ofpolymer across the film thickness.

[0077] Description

[0078] 875 liters of water and the desired weight of polymer, eg 125 kg,are mixed together as a discrete batch in a high speed disperser,similar to those used in the paint and pharmaceutical industries. Avariable speed pump circulates the dispersion around a ring main. Aspray arrangement, as described above is connected in parallel with thisring main. When the polymer is required by the process a valve opens sothat the ring man pressure is supplied to the spray nozzles. Excess flowreturns to the buffer tank which supplies the pump.

[0079] Testing

[0080] The water resistance of fibre-cement products were measured byrecording the drop in a water level of a water column having an initialheight of 180 mm. The water column was marked with height measurementsand rests on the fibre-cement product. In the tests conducted, theactual height of the water column was 180 mm. The water level drop wasrecorded before and after a 24 hour period.

[0081] The water column drop of an untreated exterior claddingfibre-cement product—standard Harditex exterior fibre-cement panel—over24 hours was 75 mm. A water resistant fibre-cement product adapted forexterior use achieved a water column drop of between 5 mm and 30 mm overa 24 hour period. The water resistant fibre-cement product used in thetest had 1% polymer based on the dry weight of fibre-cement. The waterresistant product was made as for the standard Harditex exterior panelexcept that Vinnapas RI 554Z (available from Wacker Polymer) was sprayedon to the fibre-cement as discussed earlier herein. Vinnapas RI554Z is apolyethylene, polyvinyl chloride, polyvinyl laurate terpolymer withsilane functional groups. Example of water permeability of a Harditexboard treated during production with Vinnapas RI 554Z Water columnpermeability, (cm/day) Position in the Position on the sheet Lift numberstack Edge Perm Centre Perm 48116 Top 0.5 0.8 48117 1.4 0.4 48118 1.40.6 45740 1.2 0.8 1.1 0.7 48116 Middle 0.1 0.3 48117 0.3 0.3 48118 0.20.1 45740 0.7 0.4 0.3 0.3 48116 Bottom 1.4 0.5 48117 0.1 0 48118 0.2545740 0.3 0.3 0.6 0.3

[0082] The Effect on Selected Physical Properties with varying PolymerContent Polymer Filtering Water Permeability [wt % of Vinnapas TimeM.o.R. Absorption Density (cm drop RI554Z] At 20″ [Mpa] (%) (g/ml) perday) CONTROL 16.89 9.40 34.90 1.28 27.47 0.5   17.67 8.80 31.67 1.2510.70 1 17.75 8.71 29.88 1.27 4.13 2 20.43 8.61 27.25 1.29 1.33 4 22.258.43 27.83 1.26 0.47

[0083] With reference to FIG. 2, a comparison of commercially availablefibreboards is made with a product produced according to the presentinvention (Identified as Monotek (45979)—1.0% Vinnapas). As can clearlybe seen, the Monotek product has superior abilities to resist wateruptake as evidenced by reduced weight gain.

[0084] The use of the water repelling agents herein describeddemonstrate the ability to significantly reduce water permeability offibre-cement products even other harsh autoclaving conditions. It willbe appreciated that the water-resistant fibre cement product is notlimited to use in wet areas but may be used in dry and wet areas.

[0085] Although the water resistant fibre-cement has been described withreference to the production of a water resistant fibre-cement board,tile and/or panel, it will be appreciated that this cement andtechnology may have broader applications to the construction industry.

[0086] Wherein the foregoing description reference has been made toelements or integers having known equivalents, then such equivalents areincluded as if individually set forth.

[0087] Although this invention has been described by way of example andwith reference to particular embodiments, it is to be understood thatmodifications and/or improvements may be made without departing from thescope or spirit of the invention.

1. A method of producing a water resistant fibre-cement product, themethod including combining a water repelling agent with a fibre-cementmaterial; forming a fibre-cement product from the combination, wherebythe water repelling agent is integrally associated with thefibre-cement.
 2. A method according to claim 1, wherein the waterrepelling agent is a long chain terpolymer derived from ethylene, vinylchloride, and/or vinyl laurate.
 3. A method according to claim 2,wherein the terpolymer includes silane based functional groups.
 4. Amethod according to claim 1, wherein the water repelling agent is addedto the fibre-cement as a dispersion and/or emulsion.
 5. A methodaccording to claim 4, wherein the dispersion and/or emulsion includesthe water repelling agent suspended in water, or in an alkaline solutionsuch as lime water.
 6. A method according to claim 1, wherein the waterresistant fibre-cement product is a water resistant fibre-cement boardtile, panel, and/or exterior cladding material.
 7. A method according toclaim 1, wherein the method includes the step of autoclaving thefibre-cement product.
 8. A method according to claim 1, wherein themethod includes a step of air curing the fibre-cement product.
 9. Awater resistant fibre-cement, wherein the fibre-cement includes a waterrepelling agent that is integrally associated with the fibre-cement. 10.A water resistant fibre-cement according to claim 9, wherein the waterrepelling agent is a long chain terpolymer derived from ethylene, vinylchloride, or vinyl laurate.
 11. A water resistant fibre-cement accordingto claim 10, wherein the terpolymer includes silane based functionalgroups.
 12. A water resistant fibre-cement according to any one of claim9, wherein the water repelling agent is in a proportion of substantially0.5% to 10%, by weight of the total materials used to produce thefibre-cement.
 13. A water resistant fibre-cement according to claim 12,wherein the water repelling agent is in a proportion of substantially0.5-2.0%, by weight of the total materials used to produce thefibre-cement.
 14. A water resistant fibre-cement according to claim 12,wherein the water repelling agent is in a proportion of substantially2-10% by weight of the total materials used to produce the fibre-cement.15. A water resistant fibre-cement according to claim 9, wherein thewater resistant quality of the product is not reduced by autoclaving.16. A water resistant fibre-cement according to claim 9, wherein theproduct may be a tile, panel and/or exterior cladding material.
 17. Aprocess for producing a water-resistant fibre-cement product, theprocess including using a terpolymer derived from ethylene, vinylchloride, or vinyl laurate, in forming a fibre cement product whereinthe terpolymer is integrally associated with the fibre-cement, andcuring the product.
 18. A process according to claim 17, wherein theproduct is cured at least partially by air curing.
 19. A process asclaimed in claim 17, wherein the product is at least partially cured byautoclaving.
 20. A process according to claim 19, wherein theautoclaving process includes the use of saturated steam at pressure. 21.A process according to claim 20, wherein the autoclaving process is inan alkaline environment.
 22. A process according to claim 20, whereinthe saturated steam is at a pressure of about 1000 Kpa.
 23. A processaccording to claim 21, wherein the alkaline environment is up to aboutpH
 13. 24. A process according to claim 17, wherein the terpolymer issprayed on to the fibre-cement during formation of the fibre-cement.